[21/26] mm: fix wrong vmap address calculations with odd NR_CPUS values

From: Greg KH
Date: Mon Aug 15 2011 - 22:54:24 EST

3.0-stable review patch. If anyone has any objections, please let us know.


From: Clemens Ladisch <clemens@xxxxxxxxxx>

commit f982f91516fa4cfd9d20518833cd04ad714585be upstream.

Commit db64fe02258f ("mm: rewrite vmap layer") introduced code that does
address calculations under the assumption that VMAP_BLOCK_SIZE is a
power of two. However, this might not be true if CONFIG_NR_CPUS is not
set to a power of two.

Wrong vmap_block index/offset values could lead to memory corruption.
However, this has never been observed in practice (or never been
diagnosed correctly); what caught this was the BUG_ON in vb_alloc() that
checks for inconsistent vmap_block indices.

To fix this, ensure that VMAP_BLOCK_SIZE always is a power of two.

BugLink: https://bugzilla.kernel.org/show_bug.cgi?id=31572
Reported-by: Pavel Kysilka <goldenfish@xxxxxxxxxxxx>
Reported-by: Matias A. Fonzo <selk@xxxxxxxxxxx>
Signed-off-by: Clemens Ladisch <clemens@xxxxxxxxxx>
Signed-off-by: Stefan Richter <stefanr@xxxxxxxxxxxxxxxxx>
Cc: Nick Piggin <npiggin@xxxxxxx>
Cc: Jeremy Fitzhardinge <jeremy@xxxxxxxx>
Cc: Krzysztof Helt <krzysztof.h1@xxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>

mm/vmalloc.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)

--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -732,9 +732,10 @@ static void free_unmap_vmap_area_addr(un
#define VMAP_MIN(x, y) ((x) < (y) ? (x) : (y)) /* can't use min() */
#define VMAP_MAX(x, y) ((x) > (y) ? (x) : (y)) /* can't use max() */
+#define VMAP_BBMAP_BITS \
+ VMALLOC_PAGES / roundup_pow_of_two(NR_CPUS) / 16))


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